Birth of James Prescott Joule

James Prescott Joule was born on 24 December 1818 in Salford. An English physicist born in Salford, near Manchester, Joule worked in his family's brewery and carried out experiments in his spare time. Through careful measurements, including a famous experiment in which a paddle wheel stirred water, he demonstrated that mechanical work and heat are equivalent and measured their conversion rate. His work established the principle of conservation of energy, the first law of thermodynamics, and he also described the heating effect of an electric current. With William Thomson, later Lord Kelvin, he discovered the cooling of expanding gases known as the Joule-Thomson effect. The unit of energy, the joule, is named in his honour.

Open on the timeline